Wireless energy transfer for rechargeable batteries

ABSTRACT

A wireless energy transfer enabled battery includes a resonator that is positioned asymmetrically in a battery sized enclosure such that when two wirelessly enabled batteries are placed in close proximity the resonators of the two batteries have low coupling.

BACKGROUND

1. Field

This disclosure relates to wireless energy transfer to batteries andapparatus to accomplish such transfer.

2. Description of the Related Art

Energy or power may be transferred wirelessly using a variety of knownradiative, or far-field, and non-radiative, or near-field, techniques asdetailed, for example, in commonly owned U.S. patent application Ser.No. 12/613,686 published on May 6, 2010 as US 2010/010909445 andentitled “Wireless Energy Transfer Systems,” U.S. patent applicationSer. No. 12/860,375 published on Dec. 9, 2010 as 2010/0308939 andentitled “Integrated Resonator-Shield Structures,” U.S. patentapplication Ser. No. 13/222,915 published on March 15, 2012 as2012/0062345 and entitled “Low Resistance Electrical Conductor,” U.S.patent application Ser. No. 13/283,811 published on ______ as ______ andentitled “Multi-Resonator Wireless Energy Transfer for Lighting,” thecontents of which are incorporated by reference.

Resonators and electronics may be integrated or located next tobatteries enabling wireless energy transfer to the batteries allowingwireless charging of the battery packs. With the addition of resonatorsand control circuitry, batteries and battery packs may wirelesslycapture energy from a source and recharge without having to be preciselypositioned in a charger. The wireless batteries and battery packs may bewirelessly recharged inside the host device from an external wirelesspower source without requiring that the device be physically pluggedinto an external energy supply.

However, resonators placed next to, near, or in close proximity to eachother may interact or affect each other's parameters, characteristics,wireless energy transfer performance, and the like. When two or morebatteries enabled for wireless energy transfer are placed near oneanother the resonators of each battery may interact reducing oraffecting each batteries' ability to receive wireless energy. In a largenumber of devices batteries are placed in compartments that positionbatteries in close proximity to one another. In such devices, withoutspecial consideration the wireless enabled batteries may not be able toreceive sufficient energy due to the perturbations on the resonatorsfrom other batteries. Thus what is needed is a wirelessly enabledbattery that may be positioned in close proximity to other wirelesslyenabled batteries.

SUMMARY

A wireless energy transfer enabled battery includes a resonator. In oneaspect the resonator is positioned asymmetrically in a battery sizedenclosure such that when two wirelessly enabled batteries are placed inclose proximity the resonators of the two batteries have low coupling.

In another aspect the battery enclosure may be shaped as a standardsized battery such as a AA, AAA, D and the like.

In yet another aspect the battery may include a rechargeable batteryinside the battery sized package that may be recharged by the energycaptured by the resonator. The resonator may be formed on a flexiblesubstrate that wraps around the battery.

In an assembly of at least two resonator coils the resonator coils maybe positioned to have week coupling between one another. The resonatorscoils may be integrated into separate battery structures and may beconfigured to receive energy wirelessly. In one specific aspect theresonators may have a quality factor Q of 100 or more.

In one specific aspect a wireless enabled battery may include acylindrical battery sized enclosure having a first end and a second endwith a positive terminal on the first end and the negative terminal onthe second end. The wireless battery may include a resonator that formsloops that are coaxial with the cylindrical battery enclosure. Theresonator is positioned asymmetrically in the enclosure such that theresonator has weak coupling to another resonator of another battery whenthe other battery is in near proximity with opposite orientation.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is an isometric view of two aligned resonator coils.

FIG. 2 is an isometric view of two misaligned resonator coils.

FIG. 3 is an isometric view of two resonator coils with orthogonalorientations.

FIG. 4 is an isometric view of two aligned planar resonator coils.

FIG. 5 is an isometric view of two misaligned planar resonator coils.

FIG. 6 is a cutaway view of a wirelessly enabled battery.

FIG. 7 is a cutaway view of two wirelessly enabled batteries arranged inan antiparallel configuration.

FIG. 8 is a plot showing the coupling factor versus the vertical shiftbetween two resonator coils in two wirelessly enabled batteries in closeproximity.

FIG. 9 is a cutaway view of two wirelessly enabled batteries arranged ina parallel configuration.

DETAILED DESCRIPTION

Wireless Battery Configurations

Resonators and electronics may be integrated or located next tobatteries enabling wireless energy transfer to the batteries allowingwireless charging of the battery packs. With the addition of resonatorsand control circuitry, batteries and battery packs may wirelesslycapture energy from a source and recharge without having to be preciselypositioned in a charger. The wireless batteries and battery packs may bewirelessly recharged inside the host device from an external wirelesspower source without requiring that the device be physically pluggedinto an external energy supply.

FIG. 6 shows one example of a wireless battery comprising a magneticresonator. The example battery comprises a resonator coil 606 wrappedaround an optional block of magnetic material 608. The block of magneticmaterial 608 may be hollow and may house power and control circuitry(not shown) and optionally a rechargeable battery 604 which may berecharged by the energy captured by the magnetic resonator. The magneticresonator may comprise inductors and capacitors and may comprise acoiled inductive element 606. In this example, the wireless battery isin the form factor 602 of a traditional AA battery and may be placedinto devices which normally accept a traditional AA battery. Thewireless AA battery may be charged from an external wireless energysource while in the device. In embodiments the wireless AA battery maycapture energy from an external wireless energy source and deliver thepower directly to the host device.

Wirelessly rechargeable batteries, such as the wireless AA battery shownin FIG. 6 may be placed in devices in multiple configurations. Somedevices may need only a single battery while other devices may requiretwo or more batteries which may be positioned in close proximity.Resonators in wireless batteries may therefore be required to operateindividually or in close proximity to resonators in other batteries.

Resonators placed next to, near, or in close proximity to each other mayinteract or affect each other's parameters, characteristics, wirelessenergy transfer performance, and the like. Parameters such asinductance, resistance, capacitance, and the like of the resonators andcomponents of the power and control circuitry of the resonator may bechanged or affected when a resonator is placed in close proximity toanother resonator. The effects on parameters of resonators and theirpower and control circuitry may affect the performance of the wirelessenergy transfer between the resonators in the wireless batteries and theexternal wireless energy source.

For example when a resonator is placed in close proximity to anotherresonator, the inductance of the resonator loop may be affected orperturbed. The change in inductance may perturb or detune the resonantfrequency of the resonator compared to if the resonator was isolated orfar away from any other resonator. Detuning of the resonant frequenciesof resonators transferring energy may reduce the efficiency of wirelessenergy transfer. If the detuning of the frequencies is large enough, theefficiency of energy transfer may be degraded and may decrease by 10% or50% or more. Although a change in inductance was used in this example,it should be clear to those skilled in the art that other changes inparameters of the resonator due to proximity of other resonators mayalso affect the performance of wireless energy transfer.

In applications where wireless batteries are placed in close proximityfor charging or powering devices, the proximity of resonators ofneighboring batteries may affect the parameters of the resonators,affecting their ability to receive energy from an external wirelessenergy source (i.e. reducing the amount of power or efficiency ofwireless energy transfer). In embodiments it may be desirable to have acluster or a number of resonators in near proximity without impacting orminimally impacting the parameters of wireless energy transfer to eachof the individual resonators or to the resonator ensemble.

In some embodiments it may be desirable to have resonators operate andtransfer energy with similar parameters when a resonator is far awayfrom other resonators or other wireless batteries as when in closeproximity with other resonators of other wireless batteries. In the caseof wireless batteries, for example, some devices may use only onewireless battery while other devices may use two or more wirelessbatteries arranged in close proximity. In embodiments it may bepreferable if the same wireless battery could receive energy from anexternal source with substantially the same performance and parameterswhen a single battery is charged as when a cluster or a pack ofbatteries positioned in close proximity are charged.

The inventors have discovered several methods and designs formaintaining the parameters of wireless energy transfer when a wirelessbattery is charged alone or in a group in close proximity with otherwireless batteries. In some embodiments, the wireless batteries mayinclude an active tuning capability to maintain their parameters andcompensate for any perturbations that may be caused by other resonatorsin close proximity. In other embodiments the resonators in wirelessbatteries may be statically tuned to compensate for perturbations due tothe resonators of other wireless batteries in close proximity. Inanother embodiment, the resonators in the wireless batteries may bepositioned to reduce or minimize the perturbations on the resonators ofneighboring batteries even when they are in close proximity.

Reducing Effects of Perturbations with Static Resonator Tuning inWireless Batteries

In some embodiments, resonators and resonators assemblies may bedesigned and tuned to function in close proximity to other resonators.Resonators or resonator assemblies may be designed or tuned to have thedesired parameters when in the near proximity of other resonators. Forexample, resonators and resonator assemblies may be designed andpre-tuned such that any perturbations due to the proximity of anotherresonator perturbs the parameters of the pre-tuned resonator to thedesired value and/or operating point. In embodiments, a device resonatormay be pre-tuned to have a resonant frequency that is lower than asource resonator when it is by itself but that may increase to match thesource resonator frequency when another resonator of another wirelessbattery is brought close to the device resonator. The parameters of aresonator may be pre-tuned such that the parameter values are lower orhigher than the desired or optimal parameters for energy transfer whenthe resonator is not in close proximity to other resonators. Theparameters of a resonator may be pre-tuned such that a perturbation dueto another resonator or another wireless battery in close proximitychanges the non-optimal parameters of the resonator to the desiredparameters and/or to optimal parameters.

Resonators in wireless batteries may be designed with a resonantfrequency that is lower or higher than the desired operating frequency.The lower or higher frequency may be designed to differ from a desiredoperating frequency by the same amount that a perturbation due toanother resonator is expected to cause. A resonator designed with anintrinsic resonant frequency may therefore reach a perturbed resonantfrequency that is the desired operating frequency for the wireless powersystem.

A cluster of wireless batteries, each with its resonator detuned fromthe desired operating frequency when in isolation may be placed togetherin a pack or arranged in close proximity. The perturbations caused bythe resonators of other wireless batteries may detune each resonator tothe desired parameters for wireless energy transfer allowing eachresonator of each wireless battery to receive energy from an externalsource despite the perturbation.

Static detuning of resonators, pre-tuning, or tuning of resonators tocompensate for some or any perturbations due to other resonators may beadvantageous in applications where the relative position andconfiguration of different resonators is fixed, partially fixed, orrelatively static. In an environment or application where the resonatorsand resonator assemblies may be arranged or positioned in more than oneconfiguration relative to other resonators, the static tuning approachmay result in non-constant characteristics of performance since oneconfiguration may perturb the resonator differently than anotherconfiguration of resonators.

Reducing Effects of Perturbations with Active Resonator Tuning inWireless Batteries

In another embodiment, resonators and resonator assemblies may bedesigned with an active tuning capability. In embodiments the resonatoror resonator assembly inside wireless batteries may include tunablecomponents that may adjust the parameters of the resonators and wirelessenergy transfer to maintain the parameters of wireless energy transferin the presence of perturbations. Tunable components may includecapacitors, inductors, amplifiers, resistors, switches, and the like,which may be continuously or periodically adjusted to maintain one ormore wireless energy transfer parameters. For example, the resonantfrequency of a resonator may be adjusted by changing the capacitancecoupled to the resonator coil. When the resonator's resonant frequencyis perturbed from its nominal value due to the presence of anotherresonator the resonant frequency may be adjusted by adjusting thecapacitor. Active tuning may be used to compensate for differentperturbations that may be caused by different orientations andpositioning of the resonators.

In embodiments, active tuning of resonators in wireless batteries mayallow a wireless battery to have similar parameters when it is used as asingle battery in a device, as when in a cluster or pack of resonatorswherein the parameters of the resonators may be perturbed by otherresonators of the wireless batteries.

Reducing Effects of Perturbations with Positioning in Wireless Batteries

In embodiments resonators may be located in close proximity to oneanother with minimal or acceptable effect on resonator parameters if theresonators are designed and positioned to have weak coupling betweeneach other. Resonators may be in close proximity with weak coupling ifthe resonators are oriented and positioned within or close to positionswith low mutual inductance (“null spots”) or areas with low magneticfield amplitudes.

For example, consider two capacitively loaded loop resonators comprisingconcentric loops of a conducting material as the inductive elements ofthe resonators. When two such resonator loops are brought in closeproximity in orientations and positions with strong coupling they willhave an effect on each other's parameters. For example, if the resonatorcoils 102,104 are placed in close proximity and oriented coaxially asdepicted in FIG. 1, the presence of the other resonator may affect theinductance of the resonator coil and may ultimately perturb its resonantfrequency. However, resonator coils may be in close proximity withdecreased perturbations by positioning and orienting the resonators suchthat they have weak coupling. For example, when the resonator coils 102,104 are repositioned to be off center from one another as depicted inFIG. 2, their coupling coefficient and the strength of the perturbationsmay decrease. In another example, the two resonator coils may bepositioned orthogonally to one another to reduce coupling and/orperturbations as depicted in FIG. 3. Positioning the two resonators suchthat they have low coupling with one another reduces the perturbationseach resonator causes to the other. In the offset configuration of FIG.2 or the orthogonal configuration of FIG. 3, the two resonators may beused to efficiently receive energy from an external energy source (notshown) without the need for static detuning or active tuning of theresonators to compensate for perturbations.

Similar positioning techniques may be used with other types or designsof resonators such as for planar resonator coils comprising electricalconductors 402 wrapped around blocks of magnetic material 404. When twosuch resonators 406, 408 are placed in close proximity as depicted inFIG. 4 they will have strong coupling and may perturb each other'sparameters. However if the resonators 406, 408 are misaligned asdepicted in FIG. 5, the coupling between the two resonators may decreaseand the perturbations on the parameters of the resonators may alsodecrease.

In embodiments, to reduce the effects of perturbations on resonators innear proximity, the resonators may be purposefully positioned such thatthey have weak coupling. Resonators may generally have weak coupling inareas with low magnetic field strengths and it areas where thedirectionality of the flux lines crossing the inductive elements isvarying. For example, in the resonator arrangement shown in FIG. 2,there exists a null in the coupling coefficient between the tworesonators when the amount of flux generated from within one inductiveelement and crossing the other, is equal and opposite to the amount offlux generated outside of that one inductive element and crossing theother. Resonators with this type of positioning may be referred to asbeing in a “null spot” or “null region”. The exact location andorientation where resonators and resonator assemblies have weak couplingmay be determined experimentally, numerically, analytically, and thelike.

Placement of resonators in areas of weak coupling may allow a resonatorto operate with similar performance and parameters when far away fromother resonators as when in close proximity with other resonatorswithout requiring static detuning and/or active tuning In embodimentsplacement of resonators in areas of weak coupling may allow a resonatorto operate with similar performance and parameters when far away fromother resonators as when in close proximity with other resonators with areduced or limited tuning capability.

In embodiments, the positioning technique which reduces perturbations onresonators in near proximity to each other may decrease the requiredtuning range of the resonators with active tuning and may reduce thecost and complexity of such systems.

In many devices, batteries are fixed or oriented in a predictableconfiguration and/or orientation. In devices using AA batteries forexample, multiple batteries are often arranged in parallel, andpositioned next to one another with alternating polarities (theantiparallel configuration) of their terminals 702, 704 as shown in FIG.7. The resonator of a AA battery may be designed with certain sizes,positions, and orientations within the battery to reduce or minimize theperturbations on the resonators inside the batteries when two or morebatteries are placed in close proximity to one another in particularorientations.

To reduce perturbations, resonators coils 706 and magnetic materials 708in batteries may be sized and positioned asymmetrically inside a batterysuch that when two batteries are positioned in close proximity withreversed polarities the two resonator coils 706, 712 are misaligned. Themisalignment of the resonators may be designed such that when in closeproximity to each other, and in the orientation shown in FIG. 7, theneighboring misaligned resonators are in the areas of weak couplingbetween one another similar to the structures depicted in FIGS. 2 and 5,and therefore may have reduced or small perturbations on the parametersof the resonators.

For example, the coupling factor plot versus asymmetry of one embodimentof resonator coils in an AA battery form factor is shown in FIG. 8 forthe position and configuration of batteries shown on the right of FIG.8. The plot shows the coupling factor, k, between two resonators as theoffset (or misalignment) D between the resonator coils 802 and magneticmaterials 804 is varied. Note that at approximately 1.3 mm ofdisplacement, D, the coupling factor reaches zero. At this node point,or null point, or point of zero coupling, the parameters of theresonator are practically unaffected by the presence of the resonator inthe neighboring battery. In this example, the resonant frequency of theresonators stayed substantially the same when the resonators were in theconfiguration shown in FIG. 8 as when they were separated from eachother by significant distances. Likewise, when the resonators weredisplaced by 1.3 mm, there was very little change in the quality factorsof the resonators when the batteries were in isolation (Q-118) and inthe configuration shown in FIG. 8 respectively (Q-108).

The relatively asymmetric alignment of the resonators in the batteriesallows the resonators to function and capture energy from an externalsource resonator with high efficiency in the configuration of multicellpacks and in independent configurations where the batteries are not innear proximity to other resonators. Therefore, a single battery designmay be used in multiple configurations with similar wireless energytransfer characteristics. Such a design is advantageous as it preservesat least one of the desirable characteristics of a known battery formfactor such as a AA, which is the ability to place batteries in multiplepositions within their host devices, and to know that batteryperformance is predictable in single-battery and multi-batteryarrangements.

In some embodiments, multicell battery configurations may have otherconfigurations than the one shown in FIG. 7. For example, in someapplications all the batteries may be aligned with the same polaritysuch that all of the positive terminals are on the same side. Theposition and design of the batteries may be adapted to operate in theseconfigurations.

In one embodiment, the batteries may come in two or more configurationsdepending on the orientation and position of batteries in the hostdevice battery compartment. For example, in the configuration where allthe batteries are aligned with the same polarity facing in onedirection, two different battery configurations may be used. One type ofbattery may have the resonator coil 908 and magnetic material 912positioned asymmetrically towards its positive terminal 910 while asecond type of battery may have the resonator coil 904 and magneticmaterial 906 positioned asymmetrically towards the negative terminal 902of the battery as shown in FIG. 9. In such embodiments, the batteriesmay comprise additional markings to distinguish them. For example, thebatteries may be color coded or the end terminals may be shaped toindicate whether the batteries are designed to operate as positioned inFIG. 7 or as positioned in FIG. 9. One of ordinary skill in the art willunderstand that a variety of marking schemes may be used to distinguishthe battery types, and that a number of battery types may be desirableto address common multi-cell configurations, orientations and positions.Alternating the batteries in a multi-cell configuration may allow theresonators to be in the weak coupling regions of other resonators whenin close proximity to other resonators.

In other embodiments the position of the resonator may be adjustableallowing the user to position the resonator up or down on the battery.The resonator may be mounted on a movable sleeve for example with twopositions. For multi-cell configurations with alternating orientationsof batteries, the sleeves with the resonator may be all positioned onone end of the battery. For multi-cell configurations with the batteriesall oriented in the same direction the position may be alternated foreach alternate battery.

In other embodiments, batteries may be equipped with metallic and/ormagnetic shields to prevent their interaction with neighboring batteriesor devices. These shields may be oriented so as to prevent the presenceof another battery from changing the resonant frequency of the firstbattery and vice versa. These shields may be asymmetric so that the usermay rotate the batteries so as to shield from neighboring batteries, butnot to shield from the power source.

In yet other embodiments batteries may have configurable or switchablepolarities. In embodiments the positive and negative ends or terminalsof a battery may be reversed. Resonator position and orientation insidebatteries may be fixed in an asymmetric position and the relativeposition of the resonators in close proximity to one another may bealternated by rotating the batteries. The appropriate polarity of theterminals may be chosen depending on the requirement of the applicationwith an adaptor, switch, and the like.

In embodiments, the batteries may comprise automatic positioningmechanisms that automatically move the resonators within the batterycasing so that they are positioned for maximum energy transferefficiency when in close proximity to other resonators. For example, theresonators may comprise permanent magnets that are positioned to repeleach other and move the resonators of adjacent batteries away from eachother. In other embodiments, the batteries may comprise field sensors,voltage sensors, current sensors, power sensors, and the like, and thesesensors may be used in positioning systems to move the magneticresonators within the battery structure to improve wireless powertransfer efficiency. In yet other embodiment, the sensors may be used togive feedback to a user installing the batteries to twist or turn thebattery packs, or somehow alter the relative positions and orientationsto improve wireless energy transfer performance. In embodiments, sensorsmay be used to indicate to a user that certain battery configurationsare problematic.

The asymmetrical positioning of resonators in batteries may be used invarious battery styles and sizes. Although the example described an AAbattery configurations those skilled in the art will appreciate thattechniques may be adapted to any number of different battery styles andmay be adapted to various arrangements of battery packs comprisingmultiple individual batteries.

Other Applications

Those skilled in the art will appreciate that the techniques describedlimiting perturbations in batteries in close proximity may be used inmany other applications. The techniques may be used in any applicationswhere multiple device resonators may be placed in close proximity or ina proximity close enough that they can affect each other's parameters.

For example, multiple devices with wireless device resonators may needto be positioned to reduce the perturbations on other like devices innear proximity when multiple devices are placed on or near a wirelessenergy source. In embodiments the source may be configured to haveslots, channels, markers, outlines, and the like that force or positionmultiple devices in positions and orientations where the resonators ofeach device has weak coupling to other device resonators in nearproximity.

It is to be understood that close proximity or close to one another isnot an absolute measure of distance but depends on the relative size ofresonators, the types of resonators, their power transfer levels and thelike. In embodiments, resonators may be considered in close proximitywhen they are separated by less than one characteristic size of thelargest resonator in the system. In other embodiments, resonators may beconsidered in close proximity when they are separated by two or by threecharacteristic sizes of the largest resonator in the system. In someembodiments resonators may be considered to be in close proximity whenthe resonators are close enough to perturb each other's parameters toaffect efficiency of wireless energy transfer by at least 5%.

It is to be understood that weak coupling as used in this disclosuredoes not refer to an absolute coupling metric but a relative couplingvalue. An area of weak coupling should be understood to be an area wherethe coupling is at least two times smaller than the largest possiblecoupling for the two resonators at the fixed separation distance.

While the invention has been described in connection with certainpreferred embodiments, other embodiments will be understood by one ofordinary skill in the art and are intended to fall within the scope ofthis disclosure, which is to be interpreted in the broadest senseallowable by law. For example, designs, methods, configurations ofcomponents, etc. related to transmitting wireless power have beendescribed above along with various specific applications and examplesthereof. Those skilled in the art will appreciate where the designs,components, configurations or components described herein can be used incombination, or interchangeably, and that the above description does notlimit such interchangeability or combination of components to only thatwhich is described herein.

All documents referenced herein are hereby incorporated by reference.

1. An assembly of at least two resonator coils comprising: a firstresonator coil configured for wireless energy transfer via oscillatingmagnetic fields; and a second resonator coil configured for wirelessenergy transfer via oscillating magnetic fields, wherein the assembly isconfigured such that (i) the first resonator coil is positioned in closeproximity to the second resonator coil, and (ii) the first resonatorcoil is oriented with respect to the second resonator coil in aconfiguration to achieve weak coupling. 2-17. (canceled)